Sighting apparatus



Sept? 3, 1946. p. coLBATH 2,406,807

SIGHTING APPARATUS Filed Dec. 17, 1945 4 Sheets-Sheet 1 lnvent or-z- DanL.- Cnlbath,

H is. Atbor'nes.

Sept. '3, 1946. D. 1.. COLBATH SIGHTING APPARATUS Filed Dec. 17, 1943 4Sheets-Sheet 2 F O b n e v .m

Dan L. Colbaoh, by

His Attofneg.

Sept. 3, 1946.- p. 1.. coLBATH 2,406,807

' SIGHTING APPARATUS Fil ed Dec; 17, 1943 4 Sheet s-Sheet 3 Ihvenbor:

Dan Colbath,

His Abbot-neg;

Sept. 3, 1946.

D. 1.. COLBATH I 2,406,807

SIGHTING APPARATUS 4 Sheets-Shet 4 Filed Dec. 17, 1943 Inventor:

Hi Attorney- Dan L..Co|bath,

Patented Sept. 3, 194-6 Dan L. Colbath, Schenectady, N. Y., assignor to;

General Electric Company, a corporation of New York ApplicationDecember17, 1943, Serial No. 514,591.

Claims; 1.

This invention relates. to sighting apparatus,

more particularly to sighting. apparatus which is especially useful. as.a. stadia range finder.

Stadia range. finders operate on the principle that the range of a.distant. target whose actual size is known may be determined. bymeasurement of. theangle the target subtends at the eye ofthe observer.The. subtended angle is. usually measuredby superimposingupon thev lineof sight of the. observer an imageof a stadia figure the size of which.may be adjusted,v to coincide with the known dimension of the observedtarget. When coincidenceis obtained the size. of the stadiafigure bearsa. fixed relation to. the subtended angle and target range,,.and henceadjustable means for varying. the sizeoffthe stadia figure can. becalibrated in terms. of. target range.

A stadiarangefinder is known whichcomprises a transparent. memberthrough which a target is observed. A collimating light-projectingsystem is provided. which projects an image. of a stad'ia figure so thatit isreflected from the transparent member into the observers line ofsight where it appearsas a virtual image at an infinite distance andeffectively coincident with. the observed target. Such an optical systemis described and claimed in the copendin applicationof Charles S.Grimshaw, Serial'No. 443,031, filed May 15, 1942, and. whichapplication. is assigned to the assignee of the present application.

The Grimshaw systemv includes a plurality of superimposed opaque.stadia. figure; generating plates disposed between. thev sourceof lightand the reflector and substantially in the focal plane ofthe collimatingsystem. These plates have a series of. light-conducting portionsarranged to produce a. luminous. stadia figure. formed of a plurality ofpoints of lightappearing at the intersections of. the light-conductingportions of the plates. The light-conducting portions of the plates havea configuration such. that the points of light are arranged in. acircle, the diameter of which may be varied by arelative rotative move.-mentof the plates.

A- plurality of sets of cooperating masking platesare provided which arecalibrated to determine the ranges of differentsizedtargets; that is, adifierent set must be used. for each different sized target.

This invention contemplates improvements in the Grimshaw apparatus,including an arrangement. wherein a single set of masking plates can be.used todeterminetheranges of targets. of any size. between the upper.andlower limits of. target size. for which the. device is designed;

In accordance with this invention, in one embodiment thereof}. there. isa setof'masking plates. including twoopaque plates-which haveintersectingspiral light-conductingportions. The points of. intersectionof these spiral portions define stadia. range figures in the form ofspaced dots of lightarrangedin concentric circles, the diameters ofwhich may be varied by rotating the plates relative to each other. One.plate. is rotated in accordance. withlmcwn target. size, while. the.other.

i'srotafued in accordance with target range so that;

when the proper. stadia circle coincides with the, target, the targetrange is automatically determined. A. third opaque plate. issuperimposed upon the other two and. has a series of radiallight-conducting, portions. The. plates. are arranged so that theseradial ligntr-conducting portionspass thrcughbut one of. the series ofpoints of intersection of the spiral light-conducting portionsof theother. two. plates that form. the proper circular stadiarange figure,the remaining. points of intersection. of these. spiral light-conductingportions beingmaskedout. This third plate. isalwaysmovedthroughafraction of the angle of divergence. between theother two plates, as. they are rotated. to vary the size of. the stadia.figure, so

that itsradial' linesv always-pass through the points of intersectionof. thechosen stadla figure.

For a more complete understanding of this. invention, reference.shouldbe. had to the. accompanyingdrawings in which Fig. 1 isaverticalsectional' View taken. through optical. sighting apparatus embodyingthisinvention; Fig. 2 is a horizontal sectionalview taken through theapparatus shown. in Fig. 1;,Fig...3 isa. front elevation of theapparatusshown in Figs. 1 and 2, parts being shown. in sectionandpartsbroken away so as to illustrate certaindetails of construction;Fig. 4 is an-end elevationv illustrating parts. of the stadia figuregenerating apparatus. used, in this inven tion, parts being broken awayand parts shown in section so asto illustratecertain details. ofconstruction, and.v thefigure. beingdrawn to a larger scalethan Figs. 1,2,. and 3; Fig. 5 is a sectional View taken: through the-line 55: ofFig. 4 and looking in. the: direction of the arrows; Fig. 6 is anexpanded view illustrating: the-plates and an associated member, thisfigure; being drawn to a larger scale than the preceding figures; Fig. 7is an enlarged view showing the relationship of the superimposedplateswhenadjusted for maximum target range for agiven known minimum targetsize;v Fig. 8 illustrates the. manner in which the stadia figuregeneratedby the plates shown in Fig. 7 appears to the observer; Fig; 9'is a View similar to Fig. '7 except that the plates are adjusted for ashorter range; Fig. 10 is a view similar to Fig. 8 except that thestadia figure is shown adjusted for the shorter range when the platesare in their positions shown in Fig. 9 Fig. 11 is a view similar toFigs. '7 and 9 except that it illustrates how the stadia circle isincreased for a larger target size at the same range as in Fig. 9; Fig.12 is a view similar to Figs. 8 and 10 except that it corresponds toFig. 11; and Figs. 13 and 14 are diagrammatic views illustrating theprinciple of operation of the sighting apparatus.

Referring to the drawings, there is illustrated a stadia range findingapparatus arranged in accordance with this invention and comprising atransparent reflector Ill formed of glass or some other suitablematerial through which a distant target may be observed by an observerwhose eye is positioned at I I. The plane of the transparent reflectorIll is disposed at an angle to the line of sight I2 so that an image ofa rang finding stadia figure projected along a line I3 to a collimatingreflector l4, positioned above the reflector I0, and from there backalong this line 53 to the member I is reflected from the surface of thereflector Ill into the eye of the observer where it appears as a virtualimage superimposed upon'the line of sight I2.

The reflector m is adjustably mounted upon a pair of brackets lsupported by a framework I8. This framework also supports thecollimating reflector I l, as shown. In addition, it supports a suitablelight filter Ica pivotally mounted upon a bracket Ifib for movement to aposition in the line of sight I2, as shown in full lines in Fig. 1, to aposition removed therefrom a indicated in dotted lines in this figure.

The unit including the reflector IS, the collimating reflector it, theframe l6 and the filter Ilia, is mounted upon a casing Il arranged atright angles to the unit, as shown. Mounted within the right-hand end ofthe casing IT, as viewed in Figs. 1 and 2, is a source of light I8 whichpreferably will be an electric incandescent lamp; and at the other endof the casing there is a reflector IQ for directing the light rays fromthe lamp up along the line I3 through the transparent reflector Ill tothe collimating reflector I6.

Interposed between the lamp l8 and the reflector I9 is a stadia figuregenerating apparatus 26 which is arranged to generate the stadia figureat the focal plane of the collimating reflector l4 whereby the projectedimage thereof appears to the observer to be at an infinite distance.

Thi apparatus comprises a set of three opaque disks or masking plates2I, 22 and 23, and an index plate 24, which members are shown moreclearly in Figs. 5, 6, 7, 9 and 11. The assembly of these plates ismounted within a supporting ring 25 (Figs. 4 and 5). The plates 2! and23 have a shallow pan-like shape and are mounted in the ends of thesupporting ring members 26 and 2? respectively, while the third plate221s mounted in a ring member 28, all as shown more clearly in Fig. 5.The ring 26 is mounted to rotate in an end plate 29; the ring 21 ismounted to rotate in the opposite end plate member 38; while the ring 28is mounted to rotate on the rings 26 and 21. The index plate 24 issecured to the inner end of the end plate 30.

' The main supportingring 25 and the two end plates 29 and 39 aresecured together as a unit and this unit is securedto an inturned flange31 mounted in the casing H by means of screws 32.

The rings 26 'and2l have spur gears 33 and 34' respectively attachedthereto whereby they may be rotated. Meshing with the gear 33 is apinion 35 mounted upon a shaft 36 which is journaled in the casing I!and which projects to the exterior thereof, and which on its outerprojecting end carries an adjustment knob 31. The gear 34 is driven by apinion 38 which is mounted on a shaft as also journaled in the casingI]. This shaft is driven by means of a shaft journaled in the casing l1and positioned at right angles to the shaft 39, as shown. The shafts 39and 49 are interconnected by means of bevel gears 4|. And the shaft 40projects from the casing, as shown, and on its outer end carries anadjustment knob 42. The ring 28 which supports the masking plate 22 isdriven from the rings 26 and 2'! through gears 43 and 44 formed on thetwo rings respectively and which mesh with a gear 45; this gear 45 ismounted to rotate freely upon a shaft 45a which i attached to the ring28, as shown in Fig. 5. In the specific embodiment of the inventionillustrated, the gearing is such that the ring 28 and hence the maskingplate 22 always mov through one-half of the angle of divergence betweenthe rings 26 and 21, and hence between the masking plates 2I and 23.

Mounted within the end plate 39 are a pair of light-collecting lenses45b which function to collect the light from the lamp I8 and to projectit onto the masking plates. These lenses, as shown, are secured in theend plate 30 by means of a screw plug 450.

The three opaque masking plates 2!, 22 and 23 are provided with seriesof light-conducting portions, which portions in the embodiment of theinvention illustrated in the drawings, are in the form of slots cutthrough the plates. The plate 2% is provided with a series ofradially-arranged spiral slots 66, the plate 22 with a series ofstraight radial slots ll, and the plate 23 with a series ofradially-arranged spiral slots 48 having the same shape as slots 46 butbeing conjugate to or reversely arranged with reference to them. Eachplate has the same number of light-conducting slots in its series, andin each, corresponding slots are spaced alike; and moreover, the slotsin the three series are positioned radially with reference to circularslots 49, 58 and 5| provided in the three plates 2!, 22 and 23respectively and located in their axis of rotation.

In order to secure the desired degree of sensitivity in adjustment ofthe diameter of a circle formed by the intersecting points of the spiralslots and also for the purpose of securing sharp intersecting points sothat the light-conducting areas will be small and well defined, theslots 4t and 58 have a relatively small radiu of curvature; also it isdesirable to use a relatively large number of slots 66 and 48 so as toprovide a circular stadia figure in which the dots are relatively closetogether. Because a largenumber of slots having a small radius ofcurvature are used, a given spiral slot 46 or 48 in one of the plates 2Ior 23 will intersect a number of the spiral slots in the other plate ata number of points spaced at different radial distances from the axis 0of the plates, as shownin Figs. '7, 9 and 11. For example, the slot 48a(Fig. 9) of the plate 23 intersects slots 46a, 46b, 48c and 46d of theplate 2| at the points A, B, C and D at radial distances OA, OB, OC andOD from the central axis 0. The remaining spiral slots 48 of plate 23intersect other spiral slots 46 of plate 2| in a similar way, and

therefore neglecting the effect of the third plate 22, there would beformed in the observers field central opening 4-9, --5fl and 511 It willalso -be apparentthat-asthe-pIatesZla-nd 23 are rotated' relatively toeach other these radii wii-l'kontihu ous-ly' change; For example; the"circle-of dots with'aadi'u'sOC' of- Figi 9; which" forms the stadiafigure sliw-1rin-Fig1 1'0; wi1l-be reduced in diamet er t0 gene-rate'thestadia -circleshown in Fig. 8' having a* radius-OG"b'y moving theplates-from their-positi'onsof-Fig: 9' to 'tHeir positions of? Ffge 75'Iriorder to-avoid possible con-fusion of th'e'ob server as to whichcircle ism be used fer stadia measurement it is desired-that? all butthe-proper one of th'e series-of concentric" circles "be masked ontythapl-ate 2-2 does-this: It will bBObSGIVGdbY referencetdfig: 9 that theradial slot 41dof-plate 2 2 'passes through the -peint' of'interse-cti'orr G"of-'= spiral bIOtslBdar-rdlfic, and that likewise itsco panionate radial slotspass through the other points of intersectionof the spiral I lines 46"and 41? whichdefine the stadi'a circle of Figa10, but

' that all other-points =01 intersection between the slots lfi and d'wil-l be masked out; thu-s, the-'points an'd'the slots-45a; 45b andifidwilPbe-masked "out; and-so also will all other-unwanted points-of intersection.

' When-thap-lateg 2| and; 23* areangularly ad justedwith relation toeach other, say by rotating pIate Z I counterclockwise from its positionof Fig. 9' to -its position of Fig. '7,' the' plate 22-by -vi rtueof'thefactthat "it moves-throughone-half the angle of divergence betweenthe p1ates-2-1- and 23 will 'move-its-radial line 4 Ta to alwayspass-through tlie-point of intersection (T, C betwee-nithespiral. slots48w and 46'c and again-allthe points of in tersection betweenthespiral-slotslfi and 48 will bemasked out except those lying in thecirclewh'ose radius is OC". In this way; onlyoneicircle: of dots appearsin the observers field of view-andits-diameter may be varied byrotatingthe two plates iiand 23 -re1ativelyto=each otheri:

Thearrangement of plates-'shown'in Fig. 11 cor responds-tea setting fora-larger targetsize; the

dimensions of" this target being" twice that: satin Figs. 7'"- and- 91It n ill-be observed that*in Fig.' 1 I. the slots AB interseCtthe slotsAb' and 41 at points lring on a circle whose radiusis OC.

As pointed outab'ove; in-the em-bodiment of-theinventionillustrated inthe drawings; the spiral slets Miami; 48 have' idntically tlie-samecurva-'- ture. Moreover, they: are; logarithmic-spirals; The-plate 23'hav-ingthe SlOts' 48 is adiusted 'by knob 42 in accordancewitli the-logarithm range while the? plate -2 'I having slots 46 adjusted byknob' 3T- i n accordance with the logarithm" of.itar-- get size. T6assist the nbserver in making. the 1at= t'er adju'stment, the plate'ilis calibrated in terms oftarget size in feet, for example',:1wing'span-in feet,. and is providedlwith scale slots 52ito indiecateethecalibration; Th'e sc'ale 52 'is' matched against a fii'zedreference-index 53 in the form ofa -triangular slot'formed 'in the fixedp'lateilfi; The plate -24 is providedwith a -fl'ange: 54 which masks"out-the major portion 0f the scale .52; only the indi'cia- -of thisscale adj acent-the index 5'3 being exposed; this range of the scaleisexposedby a-notch 55 fer-med in the flange-54; This-notch 55' alignswith elongated slots '56- an'd' ST for-med in the plates 22and- 2'3respectively, a'n'd' the plate 2| isprovided With an elongated slot 58which is aligned with the fixedindex 53.

In view of the foregoing, it will be understood 6 that there I will be'proj'ected into the "line- 0f P sight of the ob'server' figures which-indicate the target: si'ie matched against' an image'ofilthe index 53?all-" as show-n in Fiss8i 9and 10 The theory orop'eration maybe betterunder: stood by referencetb-Fi'gsa Band 14: The stadia ring of dots' B(Fig.13), which"spansthe outerztips of the target, has radius p. Theknownwihgspan isD, Therefore: v

New referringytoiFig. 1-4; theisl-ots d'fiii4fl-'anduMi: intersectzat=point R which lies in afcircleeofrradiusr p; .Aszthe curvature ofthe slots Mi anda 48 are: equaL the point of'intersectionPWi'11:00C1l1.:ail'0ng: a line bisecting- ;tlrret angle r}:-z whichmakesithe angle (91:02 (the:-line:O'X being: an arbitrary referencedine) Asaslot flofe diskx22- always .bisectssthe. angle z irfiimewhich-is the: angle :of sch-=- vergence betweenvdisksfl2:andr23athem whichisthe desired relationship.

rOtatedJanamOunt equal to logof" e V disk 23 is equal'to the log,K'1R;.

In. using this apparatus,- the observer firstdetermines by recognitionofthe target'tlie proper set'of the plate "2 I to be used in therangedet-ermin'ati'on; this; as pointedfout previouslxg. iseffectedb'ysetting the knob 31.. The observer then viewsthe target through thetransparent; member. l0 and. sees reflected in the line of sight animageof a" luminous stadia figure-comprisingriaiplura'lity of points arrangedin the form of .a .circle and a'luminousdotat the center of the circle,as pointed out above. This observed imageapp'ears to be at an infinitedistance. and sincei-t is superimposed upon the line of .sight by the.reflector I4 on the. transparent member l0;;it appears effectivelycoincidentlwithithe tar.- get'.. Thediameter ofthi's circle may. bevaried by'rrot atingithe knob 42 which rotatestherange plate23." Theknob 42"is' adjustedby 'tlieob server until two diametrically oppositepoints of the stadia circle are superimposed upon the outermostextremities'of a dimension of the target, such as the wing span of theaircraft shown in Figs. 8, 10 and 12. This movement'of the range plateautomatically determines the range of the target, and its movement maybe utilized in auxiliary equipment indicated by the numeral 59 driven bythe shaft 39.

While in the specific embodiment of the invention illustrated in thedrawings, the spiral lines 46 and 48 of the two plates 2| and 23 havethe same curvature, they may have different curvatures. In case they do,the masking plate 22 would not be driven at half the speeds of theplates 2| and 23, but it would be geared to them so as to be driven atsome multiple which would be satisfactory tocause its radiallight-conducting portions always to pass through the proper points ofintersection of the light-conducting portions 46 and 48 of the otherplates.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure Letters Patent of the UnitedStates is:

1. In an optical sighting device, a transparent member through which atarget may be observed, a light-projecting system for producing avirtual image of a Variable sized stadia figure in the line of sight ofthe observer by reflecting an image of said figure on said member, saidsystem comprising a source of light, a collimator, a pair ofsuperimposed opaque masking plates disposed between said source of lightand said transparent member and located in approximately the focal planeof said collimator, said masking plates having a series oflight-conducting portions arranged to intersect and thereby produce aluminous stadia figure, the proportions of which may be varied byrelative movement of said masking plates, means for rotating one of saidplates in accordance with the known dimensions of said target, and meansfor rotating the other of said plates to vary said proportions of saidstadia figure to cause said stadia figure to coincide with said targetand thereby determine the range of said target. I

2. In an optical sighting device, a transparent member through which atarget may be observed, a light-projecting system for producing a.virtual image of a variable sized stadia figure in the line of sight ofthe observer by reflecting an image of said figure on said member, saidsystem comprising a source of light, a collimator, a pair ofsuperimposed opaque masking plates disposed between said source of lightand said transparent member and located in approximately the focal planeof said collimator, said masking plates having series of spaced curvedlight-conducting portions, respectively, which are conjugate in pairs, athird superimposed opaque plate having a series of radially-extendinglight-conducting portions, means for independently rotating each of saidfirst two plates, and means 'for rotatingv said third plate responsivelyto rotation of either of said first two plates so that the third platealways takes the same predetermined angular, relationship to the othertwo plates, irrespective of the angular divergence between them, said.various light-conducting portions being arranged so that a luminousstadia figure comprising a plurality of pointsof light arranged in acircle is produced at the intersections of the light conducting portionsof said plates, the diameter of said stadia figure being variable by arelative rotation of said first two plates.

3. In an optical sighting device, a transparent member through which atarget may be observed, a light projecting system for producing avirtual image of a variable sized stadia figure in the line of sight ofthe observer by reflecting an image of said figureon said member, saidsystem comprising a source of light, a collimator, a pair ofsuperimposed opaque masking plates disposed between said source of lightand said transparent member and located in approximately-the focal planeofsaid collimator, said masking plates having series of logarithmiclight-conducting curves which are conjugate in pairs and intersect eachother at a plurality of points arranged in concentric circles, meansforrotating one of said plates in accordance with the logarithm of theknown dimensions of said target, means for rotating the other inaccordance with the logarithm of the target range, a third superimposedopaque plate having a series of radially extending lightconductingportions which intersect the curved light-conducting portions of saidfirst two plates through their points of intersection in a predeterminedone only of said concentric circles, the remainder of said circles beingmasked out by said third plate, and means for driving said third plateso that its said radial portions always bisect the angle of divergencebetween said first two'plates. i I

4.; stadia-generating apparatus comprising a pair of superimposed opaqueplates, one of said plates being provided with a series of spacedlogarithmic curved light-conducting portions that are calibrated toknown target size, and the other plate being provided with an equalnumber of spacedlogarithmic curved portions that are calibrated totarget range, the latter portions being conjugate in pairs with thefirst-named series of light-conducting portions and intersecting them soas to produce a series of light-conducting points, and means for settingsaid one.

plate'in accordance with known target size and the other in accordancewith target range.

5. stadia-generating apparatus comprising three superimposed opaqueplates, two of said plates having series of identicallyeshapedlogarithmic spiral light-conducting portions arranged conjugate in pairsso that they intersect at a' plurality of series of spaced pointsarranged in concentric circles, means for rotating one of said twoplates in accordance with the logarithm of known target size and theother plate in accordance with the logarithm of target range in order tovary the diameters of said circles, the third of said plates beingprovided with straight radial light-conducting portions that passthrough the points of intersection of said spiral.

, DAN L, ,COLBA'I'H.

